The present invention relates generally to the production of fluid from a wellbore, and particularly to a system that permits the deployment of a polished bore receptacle (PBR) and the corresponding seal stack with a single trip downhole.
A variety of equipment and devices are used in downhole, wellbore environments. In certain applications, production tubing is coupled to a packer via a polished bore receptacle that receives a seal stack disposed at the downhole end of the production tubing.
For example, a packer may be disposed within a wellbore for the production of a desired fluid, such as petroleum. Appropriate tubing extends downwardly from the packer to a gravel pack through which the production fluid flows. Typically, an inlet covered by sand screens permits the flow of production fluid into the tubing while preventing the inflow of sand and other undesirable particulate matter.
The production fluid flows upwardly through the tubing and packer into the production tubing which conducts the production fluid to a surface location or other collection point. The production tubing may have substantial length and is subject to expansion and contraction while in the wellbore. Thus, it is desirable to have a coupling between the packer and the production tubing that accommodates this movement. Often, a polished bore receptacle is latched into an upper end of the packer, and the production tubing is stung into the polished bore receptacle with an appropriate seal stack to prevent leakage between the interior of the PBR and the production tubing. A standard seal stack includes a plurality of annular spaced seals that fit within the interior of the PBR.
Conventionally, downhole deployment of the PBR and the production tubing with associated seal stack required two trips downhole. The polished bore receptacle was initially deployed downhole and latched to the packer. The seal stack and production tubing were then deployed downhole and coupled to the polished bore receptacle in a second operation, i.e. trip downhole. The need for a second trip downhole added substantial time and expense to the overall deployment operation.
Attempts have been made to deploy the PBR and seal stack in a single trip by precoupling the seal stack within the PBR. The assembled unit can then be moved downhole and latched to the packer. However, because air is trapped between the seals of the seal stack at a relatively low surface pressure, e.g. atmospheric pressure, a substantial pressure differential results once the PBR and seal stack are moved to the downhole, high pressure environment. The comparatively high external pressure tends to squeeze the PBR, thereby reducing the internal diameter of the PBR and restricting motion of the seal stack within the PBR.
It would be advantageous to have a system and method that permitted the deployment of a polished bore receptacle, seal stack and production tubing in a single trip downhole while allowing for pressure equalization between the seals of the seal stack.
The present invention features a latch for connecting a deployment tubing, having a seal stack, to a polished bore receptacle such that the deployment tubing and the polished bore receptacle may be deployed downhole simultaneously. The latch includes an outer latch housing having an interior passage of sufficient size to permit passage of a seal stack therethrough. The outer latch housing also includes a PBR connector end designed to engage the polished bore receptacle. The latch further includes an inner latch housing having a tubing connector end designed to engage the deployment tubing. Additionally, a housing coupler is connected between the outer latch housing and the inner latch housing. The housing coupler may be selectively disconnected to permit passage of the inner latch housing and the seal stack through the interior passage.
According to another aspect of the present invention, a system and method are provided for deploying a polished bore receptacle at a packer located downhole in a wellbore. The system includes a deployment tubing and a seal disposed about the deployment tubing. The system further includes a polished bore receptacle and a releasable latch. The releasable latch is coupled to the deployment tubing and to the polished bore receptacle. The design of the releasable latch permits the seal to be held outside of the polished bore receptacle during deployment. However, upon attachment of the polished bore receptacle to the packer, the releasable latch may be activated to permit insertion of the seal into the polished bore receptacle.